Patent GB-873475-A (GB)
Title: Improvements relating to firearms
Inventor: MARSH ROGER
IPC: F41G1/08
Filed: 1957-07-31
Abstract: 873,475. Firearms. WEAPONS Inc. July 31, 1957, No. 24355/57. Classes 92 and 119. The cartridge chamber and breech closure member of a firearm are mounted for relative movement longitudinally of the barrel and means are provided for causing lateral movement of the cartridge chamber in response to the relative longitudinal movement to align it with a cartridge presented for feeding to the chamber, e.g. by a magazine or feed strip, the cartridge being fed into the chamber either by movement from its position of presentation or by axial movement of the cartridge chamber over the cartridge in that position and means being provided for moving the chamber back laterally to a firing position. Means are also provided for extracting the empty cartridge case from the chamber during the relative longitudinal movement of the chamber and breech closure member. The cartridge chamber may be integral with or separate from barrel and in the former case, the barrel is arranged to pivot about an axis at right angles to its longitudinal axis in order to effect the lateral movement of the chamber. The breech closure member may be a longitudinally reciprocating breech bolt or alternatively it may take the form of a fixed breech block, in which case the barrel together with an integral cartridge chamber is arranged to reciprocate longitudinally as well as pivoting laterally. In one of many embodiments described an automatic firearm with a blowback action has a rigid frame consisting of a pair of flat, vertical, parallel longitudinal side plates 1, 2, Figs. 9, 11 of thin sheet metal, held in parallel relation by connecting bolts 6, 7 and cylindrical spacing sleeves 8. Each plate is provided with a rigid circular reinforcing collar 10, Fig. 1, at its forward end and a cover plate 12 is mounted across the top of the side plates. A peep sight 22, Fig. 11, is pivotally mounted on a spindle 23 extending between the bolt heads of the upper frame bolts 6, 7 and is spring- urged to the position shown but can be latched in a lower position adjacent the side plate 1. A cast aluminium hand grip 30, Figs. 1, 11, is mounted between the side plates by pins 31a and has a magazine opening 34 for receiving a box magazine 35. The magazine is held in position by a catch 36 on the magazine which engages a latch slide 37 provided in the hand grip portion 33, the slide being urged forwardly by a spring 38. A latch trip 39 permits disengagement of the slide 37 from the catch 36. A plastic sleeve 44, Fig. 1, is fitted on the front portions of the side plates and a plastic buttstock 45 is mounted on the rear portions of the side plates. The trigger 47 is pivotally mounted on the sleeve 8 of the lower frame bolt 7 and a pair of rollers 51 are also mounted on the sleeve 8 between the side plates 1, 2 on opposite sides of the trigger hub 48, Fig. 14, each roller being provided with a circumferential groove 52. Rollers 53, Figs. 11, 14, are mounted on the sleeve of the upper frame bolt 7 and on the sleeve of the upper and lower frame bolts 6, each roller extending between the side plates 1, 2 and being provided with circumferential grooves 54 corresponding to the grooves 52 and being located one above the other as shown. A pair of flat metal cam plates 55, 56 are mounted in the grooves 52, 54, each cam plate being provided with a cam slot 57, Fig. 9, and a trigger notch 58 at its front corner. A breech bolt 59 is mounted between the cam plates and reciprocates longitudinally therewith, the bolt and cam plates being guided for movement by the grooves 52, 54. The front portion of the trigger 47 is biased upwardly by a leaf spring 60 and comprises a T-shaped part 50 with laterally extending portions 62 adapted to engage the notches 58 in the cam plates when the breech bolt moves forwardly and the trigger is not pulled. The breech bolt 59 is substantially rectangular in cross section and has a feed rib 63, Fig. 9, extending along the bottom of the bolt for movement between the magazine lips 41 during reciprocation of the bolt to feed a cartridge from the magazine. A pair of studs 64 project from opposite sides of the bolt into openings in the cam plates 55, 56 and a safety spindle 65 is mounted for rotation in the bolt and extends into openings in the cam plates. A bolt handle 67 is connected to the spindle 65 and projects through an elongated slot 68 in the side plate 2 to permit manual'cocking of the bolt. The bolt spindle 65, Fig. 2, is cut to provide two adjacent flat faces 80, 81. Rotation of the spindle to the position shown brings the nose of the firing pin 77 forwardly beyond the bolt face 71 so that it will fire a cartridge. When the face 81 is adjacent the head 78 of the firing pin, this is the "safe" position with the nose retracted behind the face 71. Pointed lugs 83, Fig. 1, on the handle 67 discourage manipulation of the bolt when the spindle 65 is in firing position. An extractor 72 is mounted on the bolt which is also provided with a laterally offset longitudinal bore to receive an ejector rod 74, Fig. 1, passing through an opening in a back plate 84 fixed to the side plates 1, 2 and being urged forwardly by a buffer spring 91 mounted between the plate 84 and a collar 89 on the rod 74. As the bolt recoils, its rear face engages the collar 89, compresses the buffer spring 91 and moves a retaining nut 90 on the end of the rod rearwardly away from the backplate 84. A stock latch 92 on the buttstock 45 engages the plate 84 and prevents the buttstock from sliding off the rear of the gun. The cam plates 55, 56 and the breech bolt 59 are urged forward by a recoil spring assembly mounted externally of the side plate 1 and comprising a guide rod 96, Fig. 11, a recoil spring 97 and a breech bolt actuating member 98 which slides on the rod 96 in unison with the bolt 59, it being secured by a lateral lug to the cam plate 55, which lug slides in a slot provided in the side plate 2. The whole assembly is enclosed in a sheet metal cover 104. The barrel 105, Fig. 9, has an integral cartridge chamber 107 surrounded by and rigidly connected to a barrel block 108 provided with a cam follower pin 109, the ends of which engage in the cam slots 57. A trunnion block 113 is pivotally mounted between the front portions 5 of the side plates and a reduced portion 110 at the muzzle end extends through and is secured to the trunnion block 113. Thus the cam slots 57 and cam follower 109 are designed to impart a predetermined transverse swinging movement to the barrel about a front horizontal axis, the barrel moving between the loading position shown in Fig. 9 where the cartridge chamber is aligned with the top cartridge in the magazine and a firing position shown in Fig. 1 in which the chamber is aligned with the firing pin. In another embodiment, Figs. 15, 16, the assembly of reciprocating breech bolt and cam plates is replaced by a fixed breech block 139 to which are rigidly connected a pair of side plates 140. The barrel 141 is slidably mounted in a trunnion block 152 pivotally mounted between the side plates 140 and having a recess for receiving the front end 153 of a recoil spring guide rod 154. The rear portion of the guide rod is slidably mounted in a barrel block 155 which holds the guide rod parallel to the barrel while permitting sliding of the barrel relative to the rod. A recoil spring 157 is mounted on the rod 154 between a collar 156 and the barrel block 155, so that the spring is compressed as the barrel moves forwardly on firing. The barrel block 155 is rigid with the barrel and is provided with a cam pin 158 projecting laterally into cam slots 159 in the side plates 140. Cartridges 144 are mounted in a metal feed strip or feed plate 163 having equally spaced aligned openings for receiving and supporting the cartridge cases 145. The feed strip is placed between the barrel and breech block so as to provide a continuous supply of cartridges and is free to move transversely between the side plates 140. The arrangement is such on firing (see Fig. 15) the barrel moves forwardly, clears the empty cartridge case 145, swings downwardly and then recoils to engage the next cartridge in the strip (see Fig. 16). During the last moment of recoil, it swings back to the position of Fig. 15, taking the feed strip with it and the next cartridge is then in firing position. In other embodiments described having a reciprocating breech bolt and a swinging but otherwise fixed barrel, the barrel is moved transversely by a lever or a spring-urged crank operated by the bolt and by cam projections on the bolt which engage the barrel. Means are also described for preventing the feed of cartridges until the barrel is properly depressed to its loading position. In a further embodiment having a reciprocating breech bolt 180, Fig. 22, the barrel 105b is fixed both longitudinally and transversely, but is provided with a transversely reciprocating cartridge receiving chamber 108b. The reciprocating breech bolt 180 engages a cam dog 189 on a lever 183 to move the chamber 108b to the loading position shown against the action of a spring 187 which after loading returns the chamber to the firing position. In another embodiment, substantially the same as that shown in Figs. 1, 9, a rammer on the breech bolt feeds the cartridge into the chamber before the bolt reaches the magazine and a further modification of this consists in providing a separate rammer which moves forwardly in response to rearward movement of the bolt so that feeding of the cartridge is completed before the recoil spring moves the bolt forwardly. In a further embodiment the barrel 299, Fig. 33, is arranged to swing transversely, and a reciprocating breech bolt 290 and a hammertype firing mechanism are provided. The breech bolt 290 is provided with a forwardly extending portion extending over the barrel and having cut away portions forming inclined cam surfaces on its opposite sides. During movement o